26.3 Process Identification

The pid_t data type represents process IDs. You can get the
process ID of a process by calling getpid. The function
getppid returns the process ID of the parent of the current
process (this is also known as the parent process ID). Your
program should include the header files unistd.h and
sys/types.h to use these functions.

Data Type: pid_t

The pid_t data type is a signed integer type which is capable
of representing a process ID. In the GNU C Library, this is an int.